Preemptive power transfer switching

Abstract

An electrical load system includes one or more electrical loads, a power transfer switch, and an electronic control system. The power transfer switch is coupled with and can provide power to one or more electrical loads from a first power source or a second power source. The electronic control system evaluates a source impedance of the first source and controls the power transfer switch in response to the source impedance of the first source indicating a fault condition of the first power source that would interrupt power from the first power source to the one or more electrical loads prior to the fault condition disrupting power from the first power source to the one or more electrical loads.

The invention claimed is: 
     
       1. A system comprising:
 an electrical load system including: 
 one or more electrical loads; 
 a power transfer switch coupled with the one or more electrical loads and configured and operable to provide power from a first power source to the one or more electrical loads in a first switching state and to provide power from a second power source to the one or more electrical loads in a second switching state, the first power source comprising an electrical power distribution grid; and 
 an electronic control system configured and operable to: 
 evaluate a source impedance of the first power source with the power transfer switch in the first switching state, and 
 in response to the source impedance of the first power source indicating a fault condition of the first power source, control the power transfer switch to change from the first switching state to the second switching state to provide power from the second power source to the one or more electrical loads prior to the fault condition disrupting operation of the one or more electrical loads. 
 
     
     
       2. The system of  claim 1 , wherein the electronic control system is configured and operable to control the power transfer switch to change from the first switching state to the second switching state in response to an evaluation that a source impedance value violates a limit. 
     
     
       3. The system of  claim 2 , wherein the limit is dynamically modified over a learning period in response to a plurality of monitored source impedance values. 
     
     
       4. The system of  claim 2 , wherein the limit comprises an impedance drop relative to a minimum impedance value. 
     
     
       5. The system of  claim 4 , wherein the minimum impedance value is dynamically modified from an initial value in response to a plurality of monitored source impedance values. 
     
     
       6. The system of  claim 1  wherein the second power source comprises an uninterruptable power supply (UPS). 
     
     
       7. The system of  claim 1 , wherein the fault condition disrupting power from the first power source to the one or more electrical loads comprises a voltage of the first power source falling below a minimum voltage threshold. 
     
     
       8. A method comprising:
 operating an electrical load system including one or more electrical loads, a power transfer switch coupled with the one or more electrical loads and configured and operable to provide power from a first power source to the one or more electrical loads in a first switching state and to provide power from a second power source to the one or more electrical loads in a second switching state, the first power source comprising an electrical power distribution grid, and an electronic control system, said operating including: 
 evaluating a source impedance of the first power source with the power transfer switch in the first switching state, and 
 in response to the source impedance of the first power source indicating a fault condition of the first power source, controlling the power transfer switch to change from the first switching state to the second switching state to provide power from the second power source to the one or more electrical loads prior to the fault condition disrupting operation of the one or more electrical loads. 
 
     
     
       9. The method of  claim 8 , wherein the controlling the power transfer switch to change from the first switching state to the second switching state is performed in response to an evaluation that a source impedance value violates a limit. 
     
     
       10. The method of  claim 9 , wherein the limit is dynamically modified over a learning period in response to a plurality of monitored source impedance values. 
     
     
       11. The method of  claim 9 , wherein the limit comprises an impedance drop relative to a minimum impedance value. 
     
     
       12. The method of  claim 11 , wherein the minimum impedance value is dynamically modified from an initial value in response to a plurality of monitored source impedance values. 
     
     
       13. The method of  claim 8 , wherein the fault condition disrupting power from the first power source to the one or more electrical loads comprises a voltage of the first power source falling below a minimum voltage threshold. 
     
     
       14. An apparatus comprising:
 an electronic control system configured and operable to monitor and control at least in part operation of an electrical load system, the electrical load system including one or more electrical loads, and a power transfer switch coupled with the one or more electrical loads and configured and operable to provide power from a first power source to the one or more electrical loads in a first switching state and to provide power from a second power source to the one or more electrical loads in a second switching state, the first power source comprising an electrical power distribution grid, the electronic control system being configured and operable to: 
 evaluate a source impedance of the first power source with the power transfer switch in the first switching state, and 
 in response to the source impedance of the first power source indicating a fault condition of the first power source, control the power transfer switch to change from the first switching state to the second switching state to provide power from the second power source to the one or more electrical loads prior to the fault condition disrupting operation of the one or more electrical loads. 
 
     
     
       15. The apparatus of  claim 14 , wherein the electronic control system is configured and operable to control the power transfer switch to change from the first switching state to the second switching state in response to an evaluation that a source impedance value violates a limit. 
     
     
       16. The apparatus of  claim 15 , wherein the limit is dynamically modified over a learning period in response to a plurality of monitored source impedance values. 
     
     
       17. The apparatus of  claim 15 , wherein the limit comprises an impedance drop relative to a minimum impedance value. 
     
     
       18. The apparatus of  claim 17 , wherein the minimum impedance value is dynamically modified from an initial value in response to a plurality of monitored source impedance values. 
     
     
       19. The apparatus of  claim 14  comprising the electrical load system operatively coupled with the electronic control system. 
     
     
       20. The apparatus of  claim 14 , wherein the fault condition disrupting power from the first power source to the one or more electrical loads comprises a voltage of the first power source falling below a minimum voltage threshold.